Ch. 4/5: Atomic Structure Periodic Table and Periodic Trends

Periodic Table  Russian, Dmitri Mendeleev  when he arranged them by atomic mass, he found similar properties at certain intervals  published the first periodic table in 1869  left empty spaces where he predicted undiscovered elements should be  confirmed his predictions and persuaded other chemists

Periodic Table  In 1911, Henry Moseley (English) found that the pattern worked best if arranged by number of protons  Our current periodic tables use this method or arrangement

Atomic Radii  Defined by the edge of its orbital but since the edges are fuzzy, difficult to determine  Atomic Radii – half the distance between the nuclei of identical atoms that are bonded together

Atomic/Ionic Radii

Which is bigger?  Na or Rb?  Rb  Na or S?  Na  S or Te?  Te

Ionization Energy  An electron can be removed from an atom if enough energy is used  Ionization energy – the energy required to remove one electron from a gaseous neutral atom A + energy  A + + e -

Ionization Energy

Which has higher IE?  Li or F?  F  Ca or P?  P  Ba or Li?  Li

Electron Affinity Electron Affinity – the energy change when an electron is added to a gaseous neutral atom exothermic (-) exothermic (-) A + e -  A - + energy

Electron Affinity

Which has higher EA?  Ge or C?  C  In or I?  I  Mg or F?  F

Electronegativity  applies when an atom is in a compound NOT alone  Electronegativity – measure of how strongly an atom attracts electrons when it is in a compound  Fluorine (the most electronegative element) is assigned a 4.0 and then all the others were determined by comparison

Electronegativity

Which has higher electronegativity?  Sr or Be?  Be  P or O?  O  Si or Cl?  Cl